Method of fabricating a semiconductor device having a film in contact with a debonded layer

ABSTRACT

A semiconductor device in which degradation due to permeation of water and oxygen can be limited, e.g., a light emitting device having an organic light emitting device (OLED) formed on a plastic substrate, and a liquid crystal display using a plastic substrate. A layer to be debonded, containing elements, is formed on a substrate, bonded to a supporting member, and debonded from the substrate. A thin film is thereafter formed on the debonded layer. The debonded layer with the thin film is adhered to a transfer member. Cracks caused in the debonded layer at the time of debonding are thereby repaired. As the thin film in contact with the debonded layer, a film having thermal conductivity, e.g., film of aluminum nitride or aluminum nitroxide is used. This film dissipates heat from the elements and has the effect of preventing deformation and change in quality of the transfer member, e.g., a plastic substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 10/199,496, filed Jul. 22, 2002, now U.S. Pat. No. 7,045,438 nowallowed, which claims the benefit of foreign priority applications filedin Japan as Ser. No. 2001-228353 on Jul. 27, 2001 and as Ser. No.2001-300021 on Sep. 28, 2001. This application claims priority to eachof these prior applications, and the disclosures of the priorapplications are considered part of (and are incorporated by referencein) the disclosure of this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a circuitconsisted of a thin film transistor (hereinafter, referred to as TFT) inwhich the peeled off layer peeled off has been pasted and transferred ona base member and a method of manufacturing the semiconductor device.For example, the present invention relates to an electro-optic devicethat is represented by a liquid crystal module, a light emitting devicethat is represented by an EL module and an electronic equipment on whichsuch a device is mounted as a part.

It should be noted that in the present specification, the term“semiconductor device” indicates a device in general capable offunctioning by utilizing the semiconductor characteristics, and anelectro-optic device, a light emitting device, a semiconductor circuitand an electronic equipment are all semiconductor devices.

2. Related Art

In recent years, a technology constituting a thin film transistor (TFT)using a semiconductor thin film (in the range from about a few to a fewhundreds nm in thickness) formed on the substrate having an insulatingsurface has drawn attention. A thin film transistor is widely applied toelectronic devices such as an IC, an electro-optic device or the like,and particularly, there is an urgent need to be developed as a switchingelement for an image display device.

Although as for applications utilizing such an image display device, avariety of applications are expected, particularly, its utilization forportable apparatuses has drawn the attention. At present, although manyglass substrates and quartz substrates are utilized, there are defaultsof being easily cracked and heavy. Moreover, the glass substrates andquartz substrates are difficult to be made larger in therms ofconducting a mass-production, and these are not suitable for that.Therefore, the attempt that a TFT element is formed on a substratehaving flexibility, representatively, on a flexible plastic film hasbeen performed.

However, since the heat resistance of a plastic film is low, it cannothelp lowering the highest temperature of the process. As a result, atpresent, a TFT is formed which has not so excellent electriccharacteristics compared with those formed on the glass substrates.Therefore, a liquid crystal display device and light emitting elementhaving a high performance by utilizing a plastic film have not beenrealized yet.

If a light emitting device or a liquid crystal display deviceconstituted of an organic light emitting device (OLED) formed on aflexible substrate such as a plastic film can be fabricated, it can beobtained as a thin lightweight device and can be used in a displayhaving a curved surface, a show window, etc. Use of such a device is notlimited to use as a portable device, and the range of uses of such adevice is markedly wide.

However, substrates made of plastics ordinarily have permeability towater and oxygen, which act to accelerate degradation of the organiclight emitting layer. Therefore, light emitting devices using plasticsubstrates tend to have a shorter life. By considering this problem, amethod has been used in which an insulating film of silicon nitride orsilicon nitroxide is formed between a plastic substrate and an OLED toprevent mixing of water and oxygen in the organic light emitting layer.

Also, generally speaking, substrates formed of plastic film or the likeare not resistant to heat. If the temperature at which an insulatingfilm of silicon nitride or silicon nitroxide is formed on a plasticsubstrate is excessively high, the substrate deforms easily. If the filmforming temperature is excessively low, a reduction in film qualityresults and it is difficult to effectively limit permeation of water andoxygen. There is also a problem in that when a device formed on aplastic film substrate or the like is driven, heat is locally producedto deform a portion of the substrate or to change the quality thereof.

Further, if the thickness of the insulating film of silicon nitride orsilicon nitroxide is increased in order to prevent permeation of waterand oxygen, a larger stress is caused in the film and the film crackseasily. If the film thickness is large, the film cracks easily when thesubstrate is bent. Also, a layer to be debonded may crack when it isbent at the time of separation from the substrate.

SUMMARY OF THE INVENTION

In view of the above-described problems, an object of the presentinvention is to provide semiconductor device in which deterioration dueto permeation of water and oxygen can be limited, for example, a lightemitting device having an OLED formed on a plastic substrate or a liquidcrystal display device using a plastic substrate.

According to the present invention, a layer to be debonded, containingelements, is formed on a substrate, bonded to a supporting member, anddebonded from the substrate, a thin film is thereafter formed in contactwith the debonded layer, and the debonded layer with the thin film isadhered to a transfer member. The thin film is grown in contact with thedebonded layer to repair cracks caused in the debonded layer at the timeof debonding. As the thin film in contact with the debonded layer, afilm having thermal conductivity, e.g., film of aluminum nitride oraluminum nitroxide is used. This film dissipates heat from the elementsand therefore has the effect of limiting degradation of the elements aswell as the effect of preventing deformation and change in quality ofthe transfer member 22, e.g., a plastic substrate. The film havingthermal conductivity also has the effect of preventing mixing ofimpurities such as water and oxygen from the outside.

An arrangement 1 of the present invention disclosed in thisspecification is a light emitting device characterized by having, on asubstrate having an insulating surface, a light emitting element havinga cathode, an organic compound layer in contact with the cathode, and ananode in contact with the organic compound layer, an insulating film incontact with the anode, and a film formed in contact with the insulatingfilm and having thermal conductivity.

An arrangement 2 of the present invention is a light emitting devicecharacterized by having a substrate having an insulating surface, abonding layer in contact with the substrate, a film formed in contactwith the bonding layer and having thermal conductivity and an insulatingfilm in contact with the film having thermal conductivity, and a lightemitting element formed on the insulating film, the light emittingelement having a cathode, an organic compound layer in contact with thecathode, and an anode in contact with the organic compound layer.

Each of the above-described arrangements is characterized in that thefilm having thermal conductivity comprises a film transparent ortranslucent to visible light.

Also, each of the above-described arrangements is characterized in thatthe film having thermal conductivity is formed of a nitride containingaluminum, a nitroxide containing aluminum, or an oxide containingaluminum. As the film having thermal conductivity, a multilayer filmformed of a combination of films of these materials may be used. Forexample, a multilayer of aluminum nitride (AlN) and aluminum nitroxide(AlN_(X)O_(Y) (X>Y)), or a multilayer of aluminum nitroxide(AlN_(X)O_(Y) (X>Y)) and aluminum oxynitride (AlN_(X)O_(Y) (X<Y)) may beused.

Also, each of the above-described arrangements is characterized in thatthe film having thermal conductivity comprises a film containing atleast nitrogen and oxygen, and that the composition ratio of oxygen tonitrogen in the film is 0.1 to 30%.

Also, each of the above-described arrangements is characterized in thatthe substrate having an insulating surface comprises a plastic substrateor a glass substrate.

An arrangement 3 of the present invention is a semiconductor devicecharacterized by having a transfer member, a first bonding layer incontact with the transfer member, a film formed in contact with thefirst bonding layer and having thermal conductivity, an insulating filmin contact with the film having thermal conductivity, a layer containingelements on the insulating layer, a second bonding layer (a sealingmaterial or the like) in contact with the layer containing elements, anda supporting member in contact with the second bonding layer.

In the above-described arrangement, it is characterized in that if aliquid crystal display is fabricated, the supporting member is anopposed substrate, the elements are thin-film transistors connected topixel electrodes, and a space between the pixel electrodes and thetransfer member is filled with a liquid crystal material. As thetransfer member and the opposed substrate, a plastic substrate or aglass substrate may be used.

An arrangement of the present invention relating to a method offabricating a semiconductor device for realizing the structure in eachof the above-described arrangements 1 to 3 includes:

a step of forming a nitride layer on a substrate;

a step of forming an oxide layer on the nitride layer;

a step of forming an insulating layer on the oxide layer;

a step of forming a layer containing elements on the insulating layer;

a step of bonding a supporting member to the layer containing elements,and thereafter debonding the supporting member from the substrate by aphysical means at a position in the oxide layer or at an interface onthe oxide layer;

a step of forming a film having thermal conductivity on the insulatinglayer or the oxide layer; and

a step of bonding a transfer member to the film having thermalconductivity to interpose the elements between the supporting member andthe transfer member.

In this specification, “physical means” refers to a means recognized notby chemistry but by physics, more specifically a dynamic means ormechanical means having a process capable of reducing to a dynamic law,i.e., a means capable of changing some dynamic energy (mechanicalenergy). However, it is necessary that, at the time of debonding by aphysical means, the strength of bonding between the oxide layer and thenitride layer be smaller than the strength of bonding between the oxidelayer and the supporting member.

The above-described arrangement relating to the method of fabricating asemiconductor device is characterized in that the film having thermalconductivity is formed of a nitride containing aluminum, a nitroxidecontaining aluminum, or an oxide containing aluminum. As the film havingthermal conductivity, a multilayer film formed of a combination of filmsof these materials may be used.

The above-described arrangement relating to the method of fabricating asemiconductor device is also characterized in that the nitride layercontains a metallic material, and that the metallic material is a singlelayer of an element selected from the group consisting of Ti, Al, Ta, W,Mo, Cu, Cr, Nd, Fe, Ni, Co, Ru, Rh, Pd, Os, Ir, and Pt, an alloy or achemical compound having the element as a main component, or amultilayer formed of such materials.

The above-described arrangement relating to the method of fabricating asemiconductor device is also characterized in that a heat treatment or atreatment using irradiation with laser light is performed beforedebonding by the physical means.

The above-described arrangement relating to the method of fabricating asemiconductor device is also characterized in that the oxide layer is asingle layer of a silicon oxide material or a metallic oxide material,or a multilayer of these materials.

The above-described arrangement relating to the method of fabricating asemiconductor device is also characterized in that the elements arethin-film transistors having a semiconductor layer as an active layer,and that the step of forming the semiconductor layer includescrystallizing a semiconductor layer of an amorphous structure by a heattreatment or a treatment using irradiation with laser light to obtain asemiconductor layer of a crystalline structure.

The above-described arrangement relating to the method of fabricating asemiconductor device is also characterized in that if a liquid crystaldisplay is fabricated, the supporting member is an opposed substrate,the elements have pixel electrodes, and a space between the pixelelectrodes and the opposed substrate is filled with a liquid crystalmaterial.

In the above-described arrangement relating to the method of fabricatinga semiconductor device, if a light emitting device using an elementtypified by an OLED is fabricated, it is desirable that the lightemitting element be completely isolated from the outside with thesupported member used as a sealing member to prevent materials such aswater and oxygen which accelerate degradation of an organic compoundlayer from entering from the outside. Specifically, in such a case, itis characterized in that the element is a light emitting element.

In each of the above-described arrangements, to facilitate debonding, aheat treatment or a treatment using irradiation with laser light may beperformed before debonding by the physical means. In such a case, amaterial capable of absorbing laser light may be selected as thematerial of the nitride layer and the interface between the nitride andthe oxide may be heated to make separation easier. However, if laserlight is used, a transparent material is used to form the substrate.

To facilitate debonding, a granular oxide material may be provided onthe nitride layer and an oxide layer for covering the granular oxidematerial may be provided, thus making separation easier.

The transfer member referred to in this specification is a member bondedto the debonded layer after debonding. The base material of the transfermember is not particularly specified. It may be a material of anycomposition, e.g., plastic, glass, metal, or ceramics. The supportingmember referred to in this specification is a member bonded to the layerto be debonded when the layer is debonded by a physical means. The basematerial of the supporting member is not particularly specified. It maybe a material of any composition, e.g., a plastic, glass, a metal, or aceramic. The shape of the transfer member and the shape of thesupporting member are not limited to a particular one. Each of thetransfer member and the supporting member may have a flat surface or acurved surface, may be flexible, and may have the shape of a film. If itis desirable to achieve a reduction in weight with the highest priority,a plastic substrate in film form, e.g., a plastic substrate made ofpolyethylene terephthalate (PET), polyether sulfone (PES), polyethylenenaphthalate (PEN), polycarbonate (PC), nylon, polyetheretherketone(PEEK), polysulfone (PSF), polyether imide (PEI), polyallylate (PAR), orpolybutylene terephthalate (PBT) is preferred.

The present invention can be carried out without limiting the bondingmethod. Another arrangement relating to a method of fabricating asemiconductor device for realizing the structure in each of theabove-described arrangements 1 to 3 includes:

a step of forming on a substrate a layer to be debonded containingelements;

a step of bonding a supporting member to the layer to be debonded;

a step of debonding the supporting member from the substrate by aphysical means; and

a step of forming a film having thermal conductivity in contact with thelayer to be debonded.

As the debonding method in the above-described arrangements, awell-known technique can be used. Examples of such a technique are amethod in which a separation layer is provided between the layer to bedebonded and the substrate, and in which the separation layer is removedby a chemical solution (etchant) to separate the layer to be debondedfrom the substrate, and a method in which a separation layer formed ofan amorphous silicon (or polysilicon) is provided between the layer tobe debonded and the substrate, and in which the separation layer isirradiated with laser light passing through the substrate to releasehydrogen contained in the amorphous silicon, whereby a space forseparation between the layer to be debonded and the substrate is formed.In the case of separation using laser light, it is desirable that theelements contained in the layer to be debonded be formed by setting theheat treatment temperature to 410° C. or lower to avoid release ofhydrogen before debonding.

In this specification, “laser light” refers to laser light generatedfrom a laser light source, e.g., a solid-state laser such as a YAG laseror YVO₄ laser, or a gas laser such as an excimer laser. The mode oflaser oscillation may be either of continuous oscillation or pulseoscillation. Any beam shape, e.g., line irradiation or spot irradiationmay be used. Also, the scanning method is not particularly specified.

Still another arrangement relating to a method of fabricating asemiconductor device for realizing the structure in each of theabove-described arrangements 1 to 3 includes:

a step of forming on a substrate a layer to be debonded containingelements;

a step of bonding a supporting member to the layer to be debonded;

a step of attaching a flexible printed circuit (FPC) to a portion of thelayer to be debonded;

a step of fixing the supporting member by covering a connection betweenthe FPC and the layer to be debonded with an organic resin; and

a step of debonding the supporting member from the substrate by aphysical means.

The above-described arrangement includes, after the debonding step, astep of forming a film having thermal conductivity in contact with thedebonded layer, and a step of bonding a transfer member to the filmhaving thermal conductivity to interpose the debonded layer between thesupporting member and the transfer member.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A, 1B, and 1C are diagrams showing fabricating steps inaccordance with the present invention;

FIGS. 2A, 2B, and 2C are diagrams showing fabricating steps inaccordance with the present invention;

FIGS. 3A, 3B, 3C, and 3D are diagrams showing TFT fabricating steps;

FIGS. 4A, 4B, 4C, and 4D are diagrams showing TFT fabricating steps;

FIG. 5 is a diagram showing an active matrix board before enclosure;

FIGS. 6A and 6B are an external view and a cross-sectional view,respectively, of an EL module;

FIG. 7 is a cross-sectional view of an EL module;

FIG. 8 is a cross-sectional view of an EL module;

FIGS. 9A, 9B, and 9C are diagrams showing a method of forming an organiccompound layer;

FIGS. 10A, 10B, and 10C are diagrams showing LCD fabricating steps;

FIGS. 11A and 11B are diagrams showing LCD fabricating steps;

FIG. 12 is a cross-sectional view of a half-transmission type of liquidcrystal display;

FIGS. 13A to 13F are diagrams showing examples of electronic equipment;

FIGS. 14A to 14C are diagrams showing examples of electronic equipment;

FIG. 15 is a graph showing the transmittance of AlN_(X)O_(Y) film of thepresent invention;

FIG. 16 is a graph showing the results of ESCA analysis of AlN_(X)O_(Y)film of the present invention;

FIG. 17 is a graph of a MOS characteristic (AlN_(X)O_(Y) film) with BTstress; and

FIG. 18 is a graph of a MOS characteristic (SiN film) with BT stress(comparative example).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described with respect to an embodimentmode thereof.

The procedure of fabrication of a typical light emitting device usingthe present invention will be briefly described with reference to FIGS.1 and 2.

FIG. 1A illustrates a substrate 10, a nitride layer 11, an oxide layer12, a base insulating layer 13, elements 14 a to 14 c, an OLED 15, andan interlayer insulating film 16.

As the substrate 10 shown in FIG. 1A, a glass substrate, a quartzsubstrate, a ceramic substrate or the like may be used. A siliconsubstrate, a metallic substrate or a stainless substrate mayalternatively be used.

First, the nitride layer 11 is formed on the substrate 10, as shown inFIG. 1A. A nitride material containing a metallic material is used asthe nitride layer 11. A typical example of the metallic material is asingle layer of an element selected from the group consisting of Ti, Al,Ta, W, Mo, Cu, Cr, Nd, Fe, Ni, Co, Ru, Rh, Pd, Os, Ir, and Pt, an alloyor a chemical compound having the element as a main component, ormultiple layers of such materials. A single layer of a nitride of theelement, e.g., titanium nitride, tungsten nitride, tantalum nitride ormolybdenum nitride, or multiple layers of such materials may be used asthe nitride layer 11. A metallic layer formed of tungsten may be used inplace of the nitride layer 11.

Subsequently, the oxide layer 12 is formed on the nitride layer 11. Atypical example of a material used to form the oxide layer 12 is siliconoxide, silicon oxynitride or an oxide of a metal. To form the oxidelayer 12, any of film forming methods such as sputtering, plasma CVD andapplication may be used.

According to the present invention, it is important to make the oxidelayer 12 and the nitride layer 11 have different film stresses. The filmthickness of each layer is appropriately selected from the range of 1 to1000 nm to adjust the film stress in the layer. While an example of thestructure in which the nitride layer 11 is formed in contact with thesubstrate 10 and which is selected for simplification of the process isshown in FIG. 1, an insulating layer or a metallic layer capable offunctioning as a buffer layer may be formed between the substrate 10 andthe nitride layer 11 to improve the adhesion to the substrate 10.

Subsequently, a layer to be debonded is formed on the oxide layer 12.The layer to be debonded may be formed as a layer containing variouselements (a thin-film diode, a photoelectric conversion element having asilicon PIN junction, silicon resistance element, etc.) typified by aTFT. A heat treatment may be performed on the layers in such atemperature range that the substrate 10 can withstand. In the presentinvention, even though the film stress in the oxide layer 12 and thefilm stress in the nitride layer 11 are different, film separation orthe like is not caused by a heat treatment in the process of forming thelayer to be debonded. As the layer to be debonded, the elements 14 a and14 b for a drive circuit 23 and the element 14 c in a pixel portion 24are formed on the base insulating layer 13, the OLED 15 which connectselectrically to the element 14 of the pixel portion 24 is formed, andthe interlayer insulating film 16 having a thickness of 10 to 1000 nm isformed so as to cover the OLED (FIG. 1A).

If irregularities are formed in the surface after formation of thenitride layer 11 and the oxide layer 12, the surface may be flattenedbefore or after the base insulating layer is formed. Flattening has theeffect of improving coverage in the layer to be debonded and, hence, theeffect of stabilizing element characteristics in the case where thelayer to be debonded containing elements is formed. Therefore it ispreferable to perform flattening. As a treatment for this flattening,etchback, i.e., flattening by etching or the like after formation of anapplied film (resist film or the like), chemical mechanical polishing(CMP), or the like may be performed.

Subsequently, a film 17 having thermal conductivity is formed on theinterlayer insulating film 16 (FIG. 1B). The film 17 having thermalconductivity may be formed adjacently to the OLED 15 instead of beingformed on the interlayer insulating layer 16. If the film 17 is formedadjacently to the OLED 15, it is preferred that the film 17 havingthermal conductivity be an insulating film. As the film 17 havingthermal conductivity, aluminum nitride (AlN), aluminum nitroxide(AlN_(X)O_(Y) (X>Y)), aluminum oxynitride (AlN_(X)O_(Y) (X<Y)), aluminumoxide (AlO) or beryllium oxide (BeO), for example, may be used. Ifaluminum nitroxide (AlN_(X)O_(Y) (X>Y)) is used, it is preferred thatthe composition ratio of oxygen to nitride in the film be 0.1 to 30%. Itis also preferred that the film 17 having thermal conductivity be a filmtransparent or translucent to visible light. In this embodiment mode, analuminum nitride (AlN) film having a light-transmitting property andhaving a markedly high thermal conductivity of 2.85 W/cm·K and an energygap of 6.28 eV (RT) is formed by sputtering. For example, an aluminumnitride (AlN) target is used and film forming is performed in anatmosphere in which argon gas and nitrogen gas are mixed. Alternatively,film forming may be performed in a nitrogen gas atmosphere by using analuminum (Al) target. The film 17 having thermal conductivity also hasthe effect of preventing materials such as water and oxygen whichaccelerate degradation of OLED 15 from entering from the outside.

FIG. 15 shows the transmittance of AlN_(X)O_(Y) film having a thicknessof 100 nm. As shown in FIG. 15, the light-transmitting property of theAlN_(X)O_(Y) film is markedly high (the transmittance in the visiblelight region is 80 to 90%) and does not obstruct emission of light fromthe light emitting element.

According to the present invention, the AlN_(X)O_(Y) film is formed bysputtering, for example, in an atmosphere in which argon gas, oxygen gasand nitrogen gas are mixed, with an aluminum nitride (AlN) used as atarget. The AlN_(X)O_(Y) film may have several atomic percent or more,preferably 2.5 to 47.5 atm % of nitrogen. The nitrogen concentration canbe adjusted by suitably controlling sputtering conditions (substratetemperature, raw-material gas, gas flow rate, film forming pressure, andthe like). FIG. 16 shows the composition of the AlN_(X)O_(Y) filmobtained in this manner and analyzed by electron spectroscopy foranalysis (ESCA). Alternatively, film forming may be performed in anatmosphere containing nitrogen gas and oxygen gas by using an aluminum(Al) target. The film forming method is not limited to sputtering.Evaporation or any other known technique may be used.

To confirm the water/oxygen blocking effect of the AlN_(X)O_(Y) film, anexperiment was made in which a sample having an OLED sealed on a filmsubstrate with a 200 nm thick AlN_(X)O_(Y) film and a sample having anOLED sealed on a film substrate with a 200 nm thick SiN film wereprepared and changes of the samples with time in a water vaporatmosphere heated at 85 degrees were examined. The life of the OLED inthe sample having the AlN_(X)O_(Y) film was longer than that of the OLEDin the sample having the SiN film. The former OLED was able to emitlight for a longer time. From the results of this experiment, it can beunderstood that the AlN_(X)O_(Y) film is more effective than the SiNfilm in preventing materials such as water and oxygen which acceleratedegradation of the organic compound layer from entering from the outsideof the apparatus. In addition, AlN and AlN_(X)O_(Y) are more difficultto crack than SiN. Therefore, A film formed of AlN or AlN_(X)O_(Y) ismore preferable than a film formed of SiN for attaching to a plasticsubstrate.

To confirm the alkali metal blocking effect of the AlN_(X)O_(Y) film,another experiment was made in which a 50 nm thick thermally oxidizedfilm was formed on a silicon substrate; a 40 nm thick AlN_(X)O_(Y) filmwas formed on the thermally oxidized film; an aluminum electrodecontaining Li was formed on the AlN_(X)O_(Y) film; an aluminum electrodecontaining Si was formed on the silicon substrate surface opposite fromthat surface on which the films were formed; and the sample washeat-treated at 300° C. for one hour and then underwent a BT stress test(±1.7 MV/cm, 150° C., 1 hour). A MOS characteristic (C—V characteristic)was thereby measured. FIG. 17 shows the results of this experiment. Inthe C—V characteristic shown in FIG. 17, a shift in the plus directionoccurred when a plus voltage, i.e., +BT, was applied. It was confirmedtherefrom that the cause of the shift was not Li, and that theAlN_(X)O_(Y) film had an alkali metal blocking effect. For comparison,an AlLi alloy was formed on the MOS with an insulating film (100 nmthick silicon nitride film) interposed therebetween, and changes in MOScharacteristic were also examined. FIG. 18 shows the results of thisexperiment. In the C—V characteristic shown in FIG. 18, a large shift inthe minus direction occurred when a plus voltage, i.e., +BT, wasapplied. It is thought that a major cause of this shift is mixture of Liin the active layer.

A supporting member 19 for fixing the layer to be debonded to enablestripping of the substrate 10 by a physical means is adhered by using abonding layer 18 of an epoxy resin or the like (FIG. 1C). This step isbased on the assumption that the mechanical strength of the layer to bedebonded is not sufficiently high. If the mechanical strength of thelayer to be debonded is sufficiently high, the layer to be debonded canbe debonded without a supporting member on which the layer is fixed.

Subsequently, the substrate 10 on which the nitride layer 11 is formedis stripped off by a physical means. It can be stripped off by acomparatively small force since the film stress in the oxide layer 12and the film stress in the nitride layer 11 are different from eachother. While strength of bonding between the nitride layer and the oxidelayer is high enough to maintain bonding under thermal energy, the filmstresses in the nitride and oxide layers are different from each otherand a strain due to the stresses exists between the nitride and oxidelayers. Therefore, the bonding between the nitride and oxide layers isnot strong under dynamic energy and this condition is most suitable forseparation. Thus, the layer to be debonded, formed on the oxide layer12, can be separated from the substrate 10. FIG. 2A shows a state afterdebonding. This debonding method enables not only debonding of asmall-area layer to be debonded but also high-yield debonding throughthe entire area of a large-area layer to be debonded. Debonding can beperformed in the same manner even in a case where a metallic layerformed of tungsten is used in place of the nitride layer 11.

A film 20 having thermal conductivity is again formed on the surfacefrom which the substrate has been stripped off (FIG. 2B). Cracks causedat the time of debonding can be repaired by using the film 20 havingthermal conductivity. As the film 20 having thermal conductivity,aluminum nitride (AlN), aluminum nitroxide (AlN_(X)O_(Y) (X>Y)),aluminum oxynitride (AlN_(X)O_(Y) (X<Y)), aluminum oxide (AlO) orberyllium oxide (BeO), for example, may be used. It is preferred thatthe film 20 having thermal conductivity be a film transparent ortranslucent to visible light. In this embodiment mode, an aluminumnitride (AlN) film having a markedly high thermal conductivity of 2.85W/cm·K and an energy gap of 6.28 eV (RT) is formed by sputtering. Thefilm 20 having thermal conductivity also has the effect of preventingmaterials such as water and oxygen which accelerate degradation of OLED15 from entering from the outside.

The structure in which the OLED 15 is interposed between the two layersof films 17 and 20 having thermal conductivity is thus formed tocompletely isolate the OLED 15 from the outside. However, a structure inwhich only one of the two layers of films 17 and 20 is formed mayalternatively be used.

The film thickness of each of the two layers of films 17 and 20 havingthermal conductivity be set as desired in the range of 20 nm to 4 μm.

Subsequently, the debonded layer is attached to a transfer member 22 bya bonding layer 21 such as an epoxy resin. In this embodiment mode, aplastic film substrate is used as the transfer member 22 in order thatthe total weight of the light emitting device be reduced. If themechanical strength of the debonded layer is sufficiently high, it isnot necessary to specially provide the transfer member.

Thus, the light emitting device having the OLED formed on the flexibleplastic substrate is completed. Since in the structure of this lightemitting device, the elements 14 a to 14 c and the OLED 15 areinterposed between the two layers of films 17 and 20 having thermalconductivity, heat produced by the OLED 15 and the elements 14 a to 14 ccan be dissipated. The films 17 and 20 having thermal conductivity arealso capable of limiting degradation due to permeation of water andoxygen. If necessary, the supporting member or the transfer member iscut to be formed into a desired shape. A flexible printed circuit (FPC)(not shown) is attached to the debonded layer by using a well-knowntechnique. The FPC may be attached before debonding of the layer to bedebonded instead of being attached after debonding. Also, to increasethe mechanical strength of bonding between the FPC and the layer to bedebonded, an organic resin or the like may be formed to fix the FPC bycovering the bonding portion between the FPC and the layer to bedebonded.

The transfer member referred to in this specification is a member bondedto the debonded layer after debonding. The base material of the transfermember is not particularly specified. It may be a material of anycomposition, e.g., a plastic, glass, a metal, or a ceramic. Thesupporting member referred to in this specification is a member bondedto the layer to be debonded when the layer is debonded by a physicalmeans. The base material of the supporting member is not particularlyspecified. It may be a material of any composition, e.g., a plastic,glass, a metal, or a ceramic. The shape of the transfer member and theshape of the supporting member are not limited to a particular one. Eachof the transfer member and the supporting member may have a flat surfaceor a curved surface, may be flexible, and may have the shape of a film.If weight saving is the top priority, a film-type plastic substrate, forexample, a plastic substrate including polyethylene terephthalate (PET),polyethersulfone (PES), polyethylene naphthalate (PEN), polycarbonate(PC), nylon, polyetheretherketone (PEEK), polysulfone (PSF),polyetherimide (PEI), polyarylate (PAR), polybutylene terephthalate(PBT), or the like is preferable.

The present invention of the above-mentioned aspect is furtherillustrated in detail by the following Embodiments.

Embodiment 1

Embodiment of the present invention will be described with reference toFIGS. 3 to 5. In this embodiment, a method of manufacturing CMOS circuitat the same time, which is complementary combining an n-channel type TFTand a p-channel type TFT on a same substrate is explained in detail.

First, the nitride layer 101, the oxide layer 102 and the baseinsulating film 103 are formed on the substrate 100, after asemiconductor film having a crystal structure was obtained, asemiconductor layers 104 to 105 isolated in a island shape are formed byetching processing in the desired shape.

As the substrate 100, the glass substrate (#1737) is used.

Moreover, as the metal layer 101, an element selected from Ti, Al, Ta,W, Mo, Cu, Cr, Nd, Fe, Ni, Co, Ru, Rh, Pd, Os, Ir and Pt, or a singlelayer consisted of alloy materials or compound materials whose principalcomponents are the foregoing elements or a lamination of these may beused. More preferably, a single layer consisted of these nitrides, forexample, titanium nitride, tungsten nitride, tantalum nitride,molybdenum nitride or a lamination of these may be used. Here, titaniumnitride film having film thickness of 100 nm is utilized by a sputteringmethod. Also, when the adhesion of the nitride layer 101 to thesubstrate 100, a buffer layer may be provided therebetween.

Moreover, as the oxide layer 102, a single layer consisted of a siliconoxide material or a metal oxide material, or a lamination of these maybe used. Here, a silicon oxide film having film thickness of 200 nm by asputtering method is used. The bond strength between the nitride layer101 and the oxide layer 102 is strong in heat treatment, the filmpeeling (also referred to as solely “peeling”) or the like does notoccur. However, it can be easily peeled off on the inside of the oxidelayer or on the interface by the physical means.

Subsequently, as a base insulating layer 103, a silicon oxynitride film(composition ratio Si=32%, O=27%, N=24% and H=17%) prepared from the rawmaterial gases SiH₄, NH₃, and N₂ 0 was formed (preferably, 10 to 200 nm)in thickness of 50 nm at 400° C. of the film formation temperature by aplasma CVD method. Subsequently, after the surface was washed by ozonewater, the oxide film of the surface was removed by dilute hydrofluoricacid (1:100 dilution). Subsequently, a silicon oxynitride film 103 b(composition ratio Si=32%, O=59%, N=7% and H=2%) prepared from the rawmaterial gases SiH₄ and N₂O was lamination-formed in thickness of 100 nm(preferably, 50 to 200 nm) at 400° C. of the film formation temperatureby a plasma CVD method, and further, a semiconductor layer (here, anamorphous silicon layer) having an amorphous structure was formed inthickness of 54 nm (preferably, 25 to 80 nm) at 300° C. of the filmformation temperature without the air release by a plasma CVD method.

In this embodiment, although the base film 103 is shown as a two-layerstructure, a single layer film of the foregoing insulating film or alayer as a structure in which two layers or more are laminated may beformed. Moreover, there are no limitations to materials for asemiconductor film, but preferably, it may be formed using a silicon ora silicon germanium (Si_(x)Ge_(1-x) (X=0.0001-0.02)) alloy or the likeby the known methods (sputtering method, LPCVD method, plasma CVD methodor the like). Moreover, a plasma CVD apparatus may be single wafer typeapparatus, or batch type apparatus. Moreover, the base insulating filmand the semiconductor film may be continuously formed in the same filmformation chamber without contacting with the air.

Subsequently, after the surface of the semiconductor film having anamorphous structure was washed, an oxide film having an extremely thinthickness of about 2 nm is formed on the surface with ozone water.

Next, nickel acetate solution containing 10 ppm of nickel in the weightconversion was coated by a spinner. A method of spreading over theentire surface with nickel element by a sputtering method instead ofcoating may be employed.

Subsequently, a semiconductor film having a crystal structure was formedby performing the heat treatment and crystallizing it. For this heattreatment, the heat treatment of an electric furnace or the irradiationof strong light may be used. In the case where it is performed byutilizing the heat treatment of the electric furnace, it may beperformed at 500° C. to 650° C. for 4 to 24 hours. Here, after the heattreatment (500° C., one hour) for dehydrogenation was carried out, asilicon film having a crystal structure was obtained by performing theheat treatment for crystallization (550° C., 4 hours). It should benoted that although here, crystallization was performed using the heattreatment by the furnace, however, the crystallization may be performedby a lamp anneal apparatus. It should be noted that here, acrystallization technology using nickel as a metal element for promotingthe crystallization of silicon is used. However, the other knowncrystallization technology, for example, solid phase crystallizationmethod or laser crystallization method may be used.

Subsequently, after the oxide film of the surface of the silicon filmhaving a crystal structure was removed by dilute hydrofluoric acid orthe like, the irradiation of the first laser beam (XeCl: wavelength 308nm) for enhancing the crystallization ratio and repairing the defaultsremained within the crystal grain is performed in the air, or in theoxygen atmosphere. For a laser beam, an excimer laser beam of 400 nm orless of wavelength, the second higher harmonic wave, the third higherharmonic wave of YAG laser are used. When the pulse laser beam havingabout 10 to 1000 Hz of repeated frequency is used, the relevant laserbeam is condensed at 100 to 500 mJ/cm² by an optical system, irradiatedwith overlap ratio of 90 to 95% and it may be made it scan the surfaceof the silicon film. Here, the irradiation of the first laser beam isperformed at repeated frequency of 30 Hz, 393 mJ/cm² of energy densityin the air. It should be noted that since it is performed in the air, orin the oxygen atmosphere, an oxide film is formed on the surface by theirradiation of the first laser beam.

Subsequently, after the oxide film formed by irradiation of the firstlaser beam was removed by dilute hydrofluoric acid, the irradiation ofthe second laser beam is performed in the nitrogen atmosphere or in thevacuum, thereby flattening the surface of the semiconductor film. Forthis laser beam (the second laser beam), an excimer laser beam having awavelength of 400 nm or less, the second higher harmonic wave, the thirdhigher harmonic wave of YAG laser are used. The energy density of thesecond laser beam is made larger than the energy density of the firstlaser beam, preferably, made larger by 30 to 60 mJ/cm². Here, theirradiation of the second laser beam is performed at 30 Hz of therepeated frequency and 453 mJ/cm² of energy density, P-V value (Peak toValley, difference between the maximum value and minimum value) of theconcave and convex in the surface of the semiconductor film is to be 50nm or less. This P-V value is obtained by an AFM (atomic forcemicroscope).

Moreover, in this embodiment, the irradiation of the second laser beamwas performed on the entire surface. However, since the reduction of theOFF-state current is particularly effective to the TFT of the pixelsection, a step of selectively irradiating may be made on the pixelsection at least.

Subsequently, a barrier layer consisted of an oxide film of total 1 to 5nm in thickness is formed by processing the surface with ozone water for120 seconds.

Subsequently, an amorphous silicon film containing argon element whichis to be gettering site is formed in film thickness of 150 nm on thebarrier layer by a sputtering method. The film formation conditions by asputtering method of this embodiment are made as 0.3 Pa of filmformation pressure, 50 (sccm) of gas (Ar) volumetric flow rate, 3 kW offilm formation power, and 150° C. of the substrate temperature. Itshould be noted that the atomic percentage of argon element contained inthe amorphous silicon film under the above-described conditions is inthe range from 3×10²⁰/cm³ to 6×10²⁰/cm³, the atomic percentage of oxygenis in the range from 1×10¹⁹/cm³ to 3×10¹⁹/cm³. Then, the gettering isperformed by carrying out the heat treatment at 650° C. for 3 minutesusing a lamp anneal apparatus.

Subsequently, after the amorphous silicon film containing argon elementthat is the gettering site was selectively removed by using the barrierlayer as an etching stopper, the barrier layer is selectively removedwith dilute hydrofluoric acid. It should be noted that since whengettering, nickel tends to easily move into the higher oxygen densityregion, it is desirable that the barrier layer consisted of an oxidefilm is removed after the gettering. In this embodiment, an example ofconducting a gettering with argon element is shown, however it is notlimited to this method. Another gettering method can also be used.

Subsequently, after a thin oxide film is formed with the ozone water onthe surface of the silicon film (also referred to as “polysilicon film”)having the obtained crystal structure, a mask consisted of a resist isformed, and the semiconductor layers 104 and 105 isolated in an islandshape is formed in the desired shape by etching processing. After thesemiconductor layer was formed, the mask consisted of the resist isremoved.

Subsequently, the oxide film was removed by an etchant containinghydrofluoric acid, and at the same time, the surface of the silicon filmwas washed, an insulating film whose principal component is silicon andwhich is to be a gate insulating film 106 is formed. In this embodiment,a silicon oxynitride film (composition ratio Si=32%, O=59%, N=7% andH=2%) is formed in thickness of 115 nm by plasma CVD method.

Subsequently, as shown in FIG. 3B, the first electrically conductivefilm 107 having film thickness of 20 to 100 nm and the secondelectrically conductive film 108 having film thickness of 100 to 400 nmare lamination-formed on the gate insulating film 106. In thisembodiment, a tantalum nitride film having film thickness of 50 nm and atungsten film having film thickness of 370 nm are laminated sequentiallyon the gate insulating film 106.

As an electrically conductive material for forming the firstelectrically conductive film and the second electrically conductivefilm, it is formed using an element selected from Ta, W, Ti, Mo, Al andCu, or alloy material or compound material whose principal component isthe foregoing element. Moreover, as the first electrically conductivefilm and the second electrically conductive film, a semiconductor filmrepresented by a polycrystal silicon film in which impurity element suchas phosphorus or the like is doped, and AgPdCu alloy may be used.Moreover, it is not limited to a two-layer structure. For example, itmay be made a three-layer structure in which a tungsten film having filmthickness of 50 nm, aluminum-silicon (Al—Si) alloy having film thicknessof 500 nm, and a titanium nitride film having film thickness of 30 nmare in turn laminated. Moreover, in the case of a three-layer structure,instead of tungsten of the first electrically conductive film, tungstennitride may be used, instead of aluminum-silicon (Al—Si) alloy of thesecond electrically conductive film, aluminum-titanium (Al—Ti) alloyfilm may be used, or instead of a titanium nitride film of the thirdelectrically conductive film, a titanium film may be used. Moreover, itmay be a single layer structure.

Next, as shown in FIG. 3C, mask 109 consisted of resists are formed bylight exposure step, the first etching processing for forming a gateelectrode and wirings is performed. As for an etching, ICP (InductivelyCoupled Plasma) etching method may be used. The film can be etched inthe desired tapered shape by appropriately adjusting the etchingconditions (electric energy applied to the coil type electrode, electricenergy applied to the electrode on the substrate side, temperature ofelectrode on the substrate side and the like). It should be noted thatas gas for an etching, chlorine based gas which is represented by Cl₂,BCl₃, SiCl₄, CCl₄ or the like, fluorine based gas which is representedby CF₄, SF₆, NF₃ or the like or O₂ can be appropriately used.

Under the first conditions given above, the edges of the films can betapered owing to the shape of the resist mask and the effect of the biasvoltage applied to the substrate side. The angle of the tapered portionis set to 15 to 45°. In order to etch the films without leaving anyresidue on the gate insulating film, the etching time is prolonged byabout 10 to 20%. The selective ratio of the silicon oxynitride film tothe W film is 2 to 4 (typically, 3), and hence the exposed surface ofthe silicon oxynitride film is etched by about 20 to 50 nm through theover-etching treatment. Through the first etching treatment, first shapeconductive layers 110 and 111 (first conductive layers 110 a and 111 aand second conductive layers 110 b and 111 b) are formed from the firstconductive film and the second conductive film. Denoted by 112 is a gateinsulating film and a region of the gate insulating film which is notcovered with the first shape conductive layers is etched and thinned byabout 20 to 50 nm.

Then the first doping treatment is performed to dope the film with an ntype impurity (donor) as shown in FIG. 3D. The doping is made by iondoping or ion implantation. In ion doping, the dose is set to 1×10¹³ to5×10¹⁴ atoms/cm². Used as the impurity element for imparting the n typeconductivity is a Group 5 element, typically phosphorus (P) or arsenic(As). In this case, the first shape conductive layers 110 and 111 serveas masks against the element used for the doping and the accelerationvoltage is adjusted appropriately (20 to 60 ke·V, for example). Theimpurity element thus passes through the gate insulating film 112 toform impurity regions (n+ region) 113 and 114. The phosphorus (P)concentration in first impurity regions (n+ region) is set to 1×10²⁰ to1×10²¹ atoms/cm³.

Then the second doping treatment is carried out as shown in FIG. 4A.This time, the film is doped with an n-type impurity (donor) in a dosesmaller than in the first doping treatment at a high accelerationvoltage. For example, the acceleration voltage is set to 70 to 120 keVand the dose is set to 1×10¹³ atoms/cm³. As a result, impurity regionsare formed inside the first impurity regions that have been formed inthe island-like semiconductor films in FIG. 3D. In the second dopingtreatment, the second conductive films 110 b and 111 b are used as masksagainst the impurity element and the impurity element reaches regionsbelow the first conductive films 110 a and 111 a. Thus formed areimpurity regions (n− region) 115 and 116 that overlap the firstconductive films 110 a and 111 a, respectively. Since the remainingfirst conductive layers 110 a and 111 a have almost the uniformthickness, the concentration difference along the first conductivelayers is not large and the concentration in the impurity regions is1×10¹⁷ to 1×10¹⁹ atoms/cm³.

The second etching treatment is then conducted as shown in FIG. 4B. Inthis etching treatment, ICP etching is employed, CF₄ and Cl₂ and O₂ aremixed as etching gas, and plasma is generated by giving RF (13.56 MHz)power of 500 W to a coiled electrode at a pressure of 1 Pa. RF (13.56MHz) power of 50 W is also given to the substrate side (sample stage) sothat a self-bias voltage lower than that of the first etching treatmentcan be applied. The tungsten film is subjected to anisotropic etchingunder these conditions so that the tantalum nitride film or the titaniumfilm serving as the first conductive layers is remained. In this way,second shape conductive layers 117 and 118 (first conductive films 117 aand 118 a and second conductive films 117 b and 118 b) are formed.Denoted by 119 is a gate insulating film and a region of the gateinsulating film which is not covered with the second shape conductivelayers 117 and 118 is further etched and thinned by about 20 to 50 nm.

Then a resist mask 120 is formed as shown in FIG. 4C so that theisland-like semiconductor layer for forming the p-channel TFT is dopedwith a p type impurity (acceptor). Typically, boron (B) is used. Theimpurity concentration in impurity regions (p+region) 121 and 122 is setto 2×10²⁰ to 2×10²¹ atoms/cm³. Thus the regions are doped with boron ina concentration 1.5 to 3 times higher than the concentration ofphosphorus that has already been contained in the regions, therebyinverting the conductive type of the regions.

The impurity regions are formed in each semiconductor layer through theabove steps. The second shape conductive layers 117 and 118 serve asgate electrodes. Thereafter, as shown in FIG. 4D, a protectiveinsulating film 123 is formed of a silicon nitride film or a siliconoxynitride film by plasma CVD. The impurity elements that is doped thesemiconductor layers are then activated for controlling the conductivitytype.

A silicon nitride film 124 is formed and subjected to hydrogenation.Hydrogen is released from the silicon nitride film 124 as a result andhydrogen diffuses to the semiconductor layers. The semiconductor layersare thus hydrogenated.

An interlayer insulating film 125 is formed of an organic insulatingmaterial such as polyimide and acrylic. A silicon oxide film formed byplasma CVD using TEOS may of course be adopted instead, but it isdesirable to choose the above organic insulating material from theviewpoint of improving levelness.

Contact holes are formed next, so that source or drain wirings 126 to128 are formed from Al, Ti, Ta or the like.

In accordance with the above processes, a CMOS circuit obtained bycombining an n-channel TFT and a p-channel TFT complementally isobtained

A p-channel TFT has a channel formation region 130, and has the impurityregions 121 and 122 that function as source regions or drain regions.

A n-channel TFT has a channel formation region 131; an impurity region116 a (gate overlapped drain: GOLD region) overlapping the gateelectrode 118 that is formed of the second shape conductive layer; animpurity region 116 b (LDD region) formed outside the gate electrode;and an impurity region 119 functioning as a source region or a drainregion.

The CMOS TFT as such can be used to form a part of a driver circuit ofan active matrix light emitting device or an active matrix liquidcrystal display device. Besides, the n-channel TFT or the p-channel TFTas above can be applied to a transistor for forming a pixel section.

Using the CMOS circuits of this embodiment in combination, a basic logiccircuit or a more intricate logic circuit (such as a signal dividercircuit, a D/A converter, an operation amplifier and a γ correctioncircuit) can be formed. It also can constitute a memory or amicroprocessor.

Embodiment 2

An example of fabrication of a light emitting device having an OLED andusing the TFTs obtained in accordance with Embodiment 1 will bedescribed with reference to FIG. 5.

FIG. 5 shows an example of a light emitting device (in a state beforesealing) having a pixel portion and a drive circuit for driving thepixel portion, the pixel portion and the drive circuit being formed onone insulating member. A CMOS circuit forming a basic unit in the drivecircuit and one pixel in the pixel portion are illustrated. The CMOScircuit can be obtained in accordance with Embodiment 1.

Referring to FIG. 5, a substrate 200, a nitride layer 201 and an oxidelayer 202 are provided. On a base insulating layer 203 formed on theelement formation substrate, the drive circuit 204 constituted of ann-channel TFT and a p-channel TFT, a switching TFT, which is a p-channelTFT, and a current control TFT, which is an n-channel TFT, are formed.In this embodiment, each of the TFTs is formed as a top gate TFT.

The n-channel TFT and p-channel TFT are the same as those inEmbodiment 1. The description for them will not be repeated. Theswitching TFT is a p-channel TFT of a structure having two channelforming regions between a source region and a drain region (double-gatestructure). In this embodiment, the structure of the switching TFT isnot limited to the double-gate structure, and the switching TFT mayalternatively have a single-gate structure in which only one channelforming region is formed or a triple-gate structure in which threechannel forming regions are formed.

A contact hole is formed in a first interlayer insulating film 207 abovethe drain region 206 of the current control TFT before a secondinterlayer insulating film 208 is formed. This is for the purpose ofsimplifying the etching step when a contact hole is formed in the secondinterlayer insulating film 208. A contact hole is formed in the secondinterlayer insulating film 208 so as to reach the drain region 206, anda pixel electrode 209 connected to the drain region 206 is formed in thecontact hole. The pixel electrode 209 functions as the cathode of theOLED and is formed by using a conductive film containing an elementbelonging to the group I or II in the periodic table. In thisembodiment, a conductive film of a compound composed of lithium andaluminum is used.

An insulating film 213 is formed so as to cover an end portion of thepixel electrode 209. The insulating film 213 will be referred to as abank in this specification. The bank 213 may be formed of an insulatingfilm containing silicon or a resin film. If a resin film is used, carbonparticles or metal particles may be added to set the specific resistanceof the resin film to 1×10⁶ to 1×10¹² Ωm (preferably 1×10⁸ to 1×10¹⁰ Ωm),thereby reducing the possibility of dielectric breakdown at the time offilm forming.

The OLED 210 is formed by the pixel electrode (cathode) 209, an organiccompound layer 211, and an anode 212. As the anode 212, a conductivefilm of a large work function, typically an oxide conductive film isused. As this oxide conductive film, indium oxide, tin oxide, zinc oxideor some other compound of these elements may be used.

In this specification, “organic compound layer” is defined as a genericname for a multilayer formed by combining with a light emitting layer ahole injection layer, a hole transporting layer, a hole blocking layer,an electron transporting layer, an electron injection layer, or anelectron blocking layer. However, the organic compound layer maycomprise a single layer of organic compound film.

The material of the light emitting layer is an organic compound materialbut not limited to a particular one. It may be a high-molecular weightmaterial or a low-molecular weight material. For example, a thin filmformed of a light emitting material capable of emitting light by dupletexcitation or a thin film formed of a light emitting material capable ofemitting light by triplet excitation may be used as the light emittinglayer.

It is effective to form a passivation film (not shown) so as tocompletely cover the OLED 210 after the formation of the anode 212. Afilm having thermal conductivity, e.g., film of aluminum nitride,aluminum nitroxide, or beryllium oxide is suitably used as thepassivation film. Also, an insulating film comprising a diamondlikecarbon (DLC) film, a silicon nitride film or a silicon nitroxide film,or a multilayer formed of a combination of such films may be used as thepassivation film.

To protect the OLED 210, steps including a step for attaching asupporting member as described above with respect to the embodiment modeand a sealing (enclosing) step are performed. Thereafter, the substrate200 on which the nitride layer 201 is formed is stripped off. An exampleof the light emitting device after this step will be described withreference to FIGS. 6A and 6B. The transfer member 22 in FIG. 2Dcorresponds to a film substrate 600.

FIG. 6A is a top view of an EL module, and FIG. 6B is a cross-sectionalview taken along the line A-A′ of FIG. 6A. Referring to FIG. 6A, a film601 having thermal conductivity (e.g., aluminum nitride film) is formedon the flexible film substrate 600 (e.g., a plastic substrate), and apixel portion 602, a source-side drive circuit 604, and a gate-sidedrive circuit 603 are formed on the film 601. The pixel portion and thedrive circuits can be obtained in the same manner as those describedabove with respect to Embodiments 1 and 2.

An organic resin 618 and a protective film 619 are provided. The pixelportion and the drive circuit portions are covered with the organicresin 618 and the surface of the organic resin 618 is covered with theprotective film 619. These portions are enclosed with a cover member 620using an adhesive. The cover member 620 is bonded as a supporting memberbefore debonding of the element layer. It is desirable that a membermade of the same material as the film substrate 600, e.g., a plasticsubstrate be used as the cover member 620, such that the cover member620 is prevented from being deformed by heat or external force. Forexample, a member which is worked so as to form a cavity (having a depthof 3 to 10 μm) as shown in FIG. 6B is used. It is also desirable thatthe cover member be further worked to form a recess (having a depth of50 to 200 μm) capable of accommodating a desiccant 621. If the EL moduleis manufactured on a gang board, the gang board may be cut after bondingbetween the substrate and the cover member. The gang board is cut with aCO₂ laser or the like so that end surfaces are aligned.

Wiring 608 is provided for transmission of signals input to thesource-side drive circuit 604 and the gate-side drive circuit 603. Avideo signal and a clock signal from a flexible printed circuit (FPC)609 provided as an external input terminal are received through thewiring 608. Although only the FPC is illustrated, a printed wiring board(PWB) may be attached to the FPC. The light emitting device described inthis specification comprises an arrangement including not only the lightemitting device main unit but also the FPC or PWB in the attached state.

The structure of the light emitting device as seen in a cross sectionwill next be described with reference to FIG. 6B. The film 601 havingthermal conductivity is formed on the film substrate 600, the insulatingfilm 610 is formed on the film 601, and the pixel portion 602 and thegate-side drive circuit 603 are formed above the insulating film 610.The pixel portion 602 is formed by a plurality of pixels including acurrent control TFT 611 and a pixel electrode 612 electrically connectedto the drain of the current control TFT 611. The gate-side drive circuit603 is formed by using a CMOS circuit having a combination of ann-channel TET 613 and a p-channel TFT 614.

These TFTs (611, 613, 614, etc.) may be fabricated in the same manner asthe n-channel TFT of Embodiment 1 and the p-channel TFT of Embodiment 1.

After the pixel portion 602, the source-side drive circuit 604 and thegate-side drive circuit 603 have been formed on one substrate inaccordance with Embodiments 1 and 2, the supporting member (cover memberin this embodiment) is bonded, the substrate (not shown) is debonded,the film 601 (e.g., aluminum nitride film) having thermal conductivityis formed on the insulating film 610, and the film substrate 600 isthereafter adhered, as shown in FIG. 1C and FIG. 2A to 2C. A bondinglayer, which is not shown, is provided between the film 601 havingthermal conductivity and the film substrate 600 to bond these films toeach other.

In the case where the cover member 620 is formed so as to have a cavityas shown in FIG. 6B, no portion of the supporting member exists adjacentto the insulating film 610 in the portion (connection portion)corresponding to the wiring lead-out terminal at the time of debondingof the element layer after bonding of the cover member 620 provided asthe supporting member, so that the mechanical strength of this portionis low. Therefore, it is desirable that the FPC 609 be attached beforedebonding and fixed by an organic resin 622.

In addition, as the insulating film provided between the TFT and theOLED, a material which not only blocks diffusion of an impurity ion suchas an alkali metal ion, an alkali earth metal ion, but also aggressivelyadsorbs the impurity ion such as an alkali metal ion and an alkali earthmetal ion may be preferable. Furthermore, a material which resists thetemperature in the following process may be more preferable. One exampleof the material suitable for these conditions includes a silicon nitridefilm containing fluorine in a large amount. The concentration of thefluorine contained in the silicon nitride film may be 1×10¹⁹/cm³ ormore, and preferably, the composition ratio of the fluorine in thesilicon nitride film may be 1 to 5%. The fluorine in the silicon nitridefilm binds to an alkali metal ion, an alkali earth metal ion, or thelike, which is adsorbed in the silicon nitride film. Another exampleincludes an organic resin film containing particles consisting of anantimony (Sb) compound, a tin (Sn) compound, or an indium (In) compound,which adsorbs an alkali metal ion, an alkali earth metal ion, or thelike, e.g. an organic resin film including particles of antimonypentoxide (Sb₂O₅.nH₂O). This organic resin film includes particles withan average particle diameter of 10 to 20 nm, and the light transmittanceof this film is very high. The antimony compounds represented by theparticles of antimony pentoxide can easily adsorb the impurity ion suchas an alkali metal ion, and alkali earth metal ion.

The pixel electrode 612 functions as the cathode of the light emittingdevice (OLED). Banks 615 are formed at opposite ends of the pixelelectrode 612, and an organic compound layer 616 and an anode 617 of thelight emitting element are formed on the pixel electrode 612.

The organic compound layer 616 (for emission of light and movement ofcarriers for causing emission of light) may be formed by freelyselecting a combination of a light emitting layer and a chargetransporting layer or a charge injection layer. For example, alow-molecular weight organic compound material or a high-molecularweight organic compound material may be used to form the organiccompound layer 616. Also, a thin film formed of a light emittingmaterial (singlet compound) capable of emission of light (fluorescence)by singlet excitation or a thin film formed of a light emitting material(triplet compound) capable of emission of light (phosphorescence) bytriplet excitation may be used as the organic compound layer 616. Aninorganic material such as silicon carbide may be used as a chargetransporting layer or a charge injection layer. These organic andinorganic materials may be selected from well-known materials.

The anode 617 also functions as a common wiring element connected to allthe pixels and is electrically connected to the FPC 609 via connectionwiring 608. All the elements included in the pixel portion 602 and thegate-side drive circuit 603 are covered with the anode 617, the organicresin 618 and the protective film 619.

It is preferred that a material higher in transparency or translucencyto visible light be used as the organic resin 618. Also, it is desirablethat a material higher in ability to limit permeation of water andoxygen be used as the organic resin 618.

Also, it is preferred that after the light emitting element has beencompletely covered with the organic resin 618, the protective film 619be at least formed on the surface (exposed surface) of the organic resin618 as shown in FIGS. 6A and 6B. The protective film may be formed onthe entire surface including the back surface of the substrate. In sucha case, it is necessary to carefully form the protective film so that noprotective film portion is formed at the position where the externalinput terminal (FPC) is provided. A mask may be used to prevent filmforming of the protective film at this position. The external inputterminal portion may be covered with a tape such as a tape made ofTeflon (registered trademark) used as a masking tape in a CVD apparatusto prevent film forming of the protective film. A film having thermalconductivity like the film 601 may be used as the protective film 619.

The light emitting element constructed as described above is enclosedwith the film 601 having thermal conductivity and the protective film619 to completely isolate the light emitting element from the outside,thus preventing materials such as water and oxygen which acceleratedegradation of the organic compound layer by oxidation from enteringfrom the outside. Also, the film having thermal conductivity enablesdissipation of produced heat. Thus, the light emitting device havingimproved reliability is obtained.

Another arrangement is conceivable in which a pixel electrode is used asan anode and an organic compound layer and a cathode are formed incombination to emit light in a direction opposite to the directionindicated in FIG. 6B. FIG. 7 shows an example of such an arrangement.This arrangement can be illustrated in the same top view as FIG. 6A andwill therefore be described with reference to a cross-sectional viewonly.

The structure shown in the cross-sectional view of FIG. 7 will bedescribed. An insulating film 710 is formed on a film substrate 700, anda pixel portion 702 and a gate-side drive circuit 703 are formed overthe insulating film 710. The pixel portion 702 is formed by a pluralityof pixels including a current control TFT 711 and a pixel electrode 712electrically connected to the drain of the current control TFT 711.After the layer to be debonded, which is formed on a substrate inaccordance with the above-described embodiment mode of the presentinvention, has been debonded, a film 701 having thermal conductivity isformed on the surface of the layer to be debonded. Further, the filmsubstrate 700 is adhered to the layer 701 having thermal conductivity. Abonding layer, which is not shown, is provided between the film 701having thermal conductivity and the film substrate 700 to bond thesefilms to each other. A gate-side drive circuit 703 is formed by using aCMOS circuit having a combination of an n-channel TET 713 and ap-channel TFT 714.

These TFTs (711, 713, 714, etc.) may be fabricated in the same manner asthe n-channel TFT 201 of Embodiment 1 and the p-channel TFT 202 ofEmbodiment 1.

The pixel electrode 712 functions as an anode of the light emittingdevice (OLED). Banks 715 are formed at opposite ends of the pixelelectrode 712, and an organic compound layer 716 and a cathode 717 ofthe light emitting element are formed over the pixel electrode 712.

The cathode 717 also functions as a common wiring element connected toall the pixels and is electrically connected to a FPC 709 via connectionwiring 708. All the elements included in the pixel portion 702 and thegate-side drive circuit 703 are covered with the cathode 717, an organicresin 718 and a protective film 719. A cover member 720 is bonded to theelement layer by an adhesive. A recess is formed in the cover member anda desiccant 721 is set therein.

In the case where the cover member 720 is formed so as to have a cavityas shown in FIG. 7, no portion of the supporting member exists adjacentto the insulating film 710 in the portion corresponding to the wiringlead-out terminal at the time of debonding of the element layer afterbonding of the cover member 720 provided as the supporting member, sothat the mechanical strength of this portion is low. Therefore, it isdesirable that the FPC 709 be attached before debonding and fixed by anorganic resin 722.

In the arrangement shown in FIG. 7, the pixel electrode is used as theanode while the organic compound layer and the cathode are formed incombination, so that light is emitted in the direction of the arrow inFIG. 7.

While the top gate TFTs have been described by way of example, thepresent invention can be applied irrespective of the TFT structure. Forexample, the present invention can be applied to bottom gate (invertedstaggered structure) TFTs and staggered structure TFTs.

Embodiment 3

While an example of use of the top gate TFT in Embodiment 2 has beendescribed, a bottom gate TFT can also be used. An example of anarrangement using a bottom gate TFT will be described with reference toFIG. 8.

As shown in FIG. 8, each of an n-channel TFT 913, a p-channel TFT 914,and an n-channel TFT 911 is of the bottom gate structure. The TFTs inthe bottom gate structure may be fabricated by using well-knowntechniques. The active layer of these TFTs may be a semiconductor filmhaving a crystalline structure (e.g., polysilicon) or a semiconductorfilm having an amorphous structure (e.g., amorphous silicon).

In FIG. 8 are illustrated a flexible film substrate 900 (e.g., a plasticsubstrate), a film 901 having thermal conductivity (e.g., aluminumnitride film), a pixel portion 902, a gate-side drive circuit 903, aninsulating film 910, a pixel electrode (cathode) 912, a bank 915, anorganic compound layer 916, an anode 917, an organic resin 918, aprotective film 919, a cover member 920, a desiccant 921, and an organicresin 922. A bonding layer, which is not shown, is provided between thefilm 901 having thermal conductivity and the film substrate 900 to bondthese films to each other.

The arrangement is the same as that of Embodiment 3 except for then-channel TFT 913, the p-channel TFT 914 and the n-channel TFT 911. Thedescription of the same details will not be repeated.

Embodiment 4

In this embodiment, when an organic compound layer is formed by an inkjet method, the organic compound layer is continuously formed through aplurality of pixels. More specifically, an example of formation in whichthe organic compound layer is formed in a stripe form on each of columnsor rows of pixel electrodes arranged in correspondence with a matrixwith m rows and n columns will be described. Also, the organic compoundlayer is formed in an oblong or rectangular shape in correspondence witheach pixel electrode.

FIGS. 9A, 9B, and 9C are diagrams illustrating this embodiment. FIG. 9Ashows an arrangement in which a pixel portion 802, a scanning-line-sidedrive circuit 803 and a data-line-side drive circuit 804 are provided ona substrate 801. A separation layer 805 is provided in the form of landsin a striped pattern in the pixel portion 802, and the organic compoundlayer is formed between each adjacent pair of the separation layerlands. The separation layer 805 is provided for the purpose ofpreventing each adjacent pair of the organic compound layer portionsfrom mixing when the organic compound layer is formed by an ink jetmethod.

The organic compound layer 806 is formed by jetting from an ink head 807a solution containing an organic compound material. The material of theorganic compound layer is not limited to a particular one. However, if amulticolor is performed, organic compound layers 806R, 806G, and 806Bmay be provided in correspondence with red, green and blue.

FIG. 9B is a cross-sectional view of the structure schematically shownin FIG. 9A, showing a state in which the scanning-line-side drivecircuit 803 and the pixel portion 802 are formed on the substrate 801.The lands of separation layer 805 are formed in the pixel portion 802,and organic compound layers 806R, 806G, and 806B are formed between theseparation layer lands. The ink head 807 is of an ink jet type. Inkdroplets 808R, 808G, and 808B corresponding to the colors, red, greenand blue are jetted from the ink head 807 according to a control signal.The jetted ink droplets 808R, 808G, and 808B are attached to the surfaceof the substrate and undergo drying and baking steps. Thereafter, thejetted materials function as the organic compound layers. The ink headmay be moved in one direction for scanning along each column or row, sothat the processing time required to form the organic compound layerscan be reduced.

FIG. 9C is a diagram showing the pixel portion in more detail. Currentcontrol TFTs 810 and pixel electrodes 812 connected to the currentcontrol TFTs 810 are formed on the substrate, and the organic compoundlayers 806R, 806G, and 806B are formed between the lands of theseparation layer 805 on the pixel electrodes. It is desirable that aninsulating film 811 having an alkali metal blocking effect be formedbetween the pixel electrodes 812 and the current control TFTs 810.

This embodiment can be applied as the method of forming the organiccompound layer in one of the embodiment mode, Embodiment 2 andEmbodiment 3.

Embodiment 5

In this embodiment, the step in which an active matrix type liquidcrystal display device is prepared by peeling off the substrate from theactive matrix substrate prepared in Embodiment 1 and adhering it with aplastic substrate will be described below. FIG. 10 is used for thepurpose of describing it.

In FIG. 10A, the reference numeral 400 denotes a substrate, thereference numeral 401 denotes a nitride layer, the reference numeral 402denotes an oxide layer, the reference numeral 403 denotes a baseinsulating layer, the reference numeral 404 a denotes an element of adriver circuit 413, the reference numeral 404 b denotes an element 404 bof the pixel section 414 and the reference numeral 405 denotes a pixelelectrode. Here, the term “element” is referred to a semiconductorelement (typically, TFT) or MIM element or the like used for a switchingelement of pixels in an active matrix type liquid crystal displaydevice. In addition, an active layer of the switching element can beboth a semiconductor having a crystal structure film (polysilicon filmand the like) and a semiconductor film (amorphous silicon and the like)having an amorphous structure.

First, according to Embodiment 1, n-channel type TFT, one of whichelectrode is a a pixel electrode, is formed. Further, N-channel TFT andp-channel TFT are formed on the driver circuit 413 respectively on thesame substrate as the substrate on which the above n-channel TFT withthe pixel electrode is formed. Subsequently, after the active matrixsubstrate of the state in FIG. 10A was obtained, an orientation film 406a is formed on the active matrix substrate of FIG. 10A, and a rubbingprocessing is performed. It should be noted that in this embodiment,before the orientation film is formed, a spacer in a column shape (notshown) for retaining a substrate interval was formed at the desiredposition by patterning an organic resin film such as an acryl resin orthe like. Moreover, instead of a spacer in a column shape, a spacer in asphere shape may be scattered over the whole surface of the substrate.

Moreover, in this embodiment, it is preferable that films that is mainlycontained Al or Ag or lamination of these films that have wellreflectivity are used for forming a pixel electrode, but when the pixelelectrode is formed by a transparent conductive film, although thenumber of photo-masks increases by one sheet, a transparent type displaydevice can be formed.

Subsequently, an opposing substrate which is to be a supporting member407 is prepared for. A color filter (not shown) in which a colored layerand a shielding layer were arranged corresponding to the respectivepixels has been provided on this opposing substrate. Moreover, ashielding layer was provided on the portion of the driver circuit. Aflattening film (not shown) for covering this color filter and theshielding layer was provided. Subsequently, an opposing electrode 408consisted of a transparent conductive film was formed on the flatteningfilm in the pixel section, an orientation film 406 b was formed on thewhole surface of the opposing substrate, and the rubbing processing wasprovided.

Then, an active matrix substrate 400 in which the pixel section and thedriver circuit were formed and the supporting member 407 are adheredtogether with a sealing medium which is to be an adhesive layer 409.Into a sealing medium, filler is mixed, two sheets of substrates areadhered together with uniform interval by this filler and a spacer in acolumn shape. Then, between both substrates, a liquid crystal material410 is implanted and completely sealed with a sealing compound (notshown) (FIG. 10B). As the liquid crystal material 410, the known liquidcrystal material may be used.

Next, the substrate 400 provided a nitride layer or a metal layer 401 ispeeled off by physical means. (FIG. 10C) The substrate 400 can be peeledoff by comparatively small power, because the membrane stress of theoxide layer 402 is different from that of the nitride layer 401.

The film 415 having the heat conductivity is formed on the face that ispeeled off. (FIG. 11A) The film 415 having the heat conductivity canrepair a crack due to peeling. As the film 415 having the heatconductivity, a nitride aluminum (AlN), an oxynitride aluminum (AlNO),and an oxynitride beryllium oxide (BeO) can be used. Further, it ispreferable for the film 415 having the heat conductivity to betransparent film or a translucent film as against visible light. In thisembodiment, the nitride aluminum (AlN) having 2.85 W/cm·K extremely highheat conductivity rate and 6.28 eV (RT) energy gap is formed bysputtering.

Subsequently, the film 415 having the heat conductivity is adhered withan adhesive layer 411 consisted of an epoxy resin or the like on atransfer member 412. In this embodiment, the transfer member 412 can bemade light by using plastic film substrate. In this way, a flexibleliquid crystal module is completed. The liquid crystal module canprevent an element from deterioration by emitting the generation of heatoccurred by elements 404 a to 404 c by using the film 415 having theheat conductivity. The film 415 having the heat conductivity can preventtransformation and a change in quality of a transfer member that is weakto heat. Then, if necessary, the flexible substrate 412 or an opposingsubstrate is cut down in the desired shape. Furthermore, a polarizingplate (not shown) or the like was appropriately provided using the knowntechnology. Then, a FPC (not shown) was attached using the knowntechnology. At the time of debonding of the element layer after bondingof the cover member 620 provided as the supporting member, so that themechanical strength of this portion is low. Therefore, it is desirablethat the FPC 609 be attached before debonding and fixed by an organicresin 622. In addition, after that the substrate is peeled off, theopposite substrate is bonded, the wiring drawing portion (a connectingportion) become only peeled off layer so that the mechanical strengthbecome weak. Thus, it is preferable that the peeled off layer is adheredover with FPC before peeling off and fixed with organic resin.

Embodiment 6

An example of a reflection type of display device in which the pixelelectrode is formed of a metallic material having a reflecting propertyhas been described as Embodiment 5. This embodiment is an example of ahalf-transmission type of display device in which pixel electrodes areformed of an conductive film having a light-transmitting property and ametallic material having a reflecting property, as shown in FIG. 12.

The step of forming the interlayer insulating layer covering the TFTsand the steps performed before this step are the same as those inEmbodiment 5, and the description for them will not be repeated. One oftwo electrodes in contact with the source region or the drain region ofa TFT is formed of a metallic material having a reflecting property toform a pixel electrode (reflecting portion) 502. Subsequently, a pixelelectrode (transmitting portion) 501 made of a conductive film having alight-transmitting property is formed so as to overlap the pixelelectrode (reflecting portion) 502. As the conductive film having alight-transmitting property, indium-tin oxide (ITO), indium-zinc oxide(In₂O₂—ZnO) or zinc oxide (ZnO), for example, may be used.

An active matrix board is formed in the above-described manner. Thesubstrate is stripped off from this active matrix board in accordancewith the embodiment mode. A film 507 having thermal conductivity isthereafter formed, a plastic substrate is bonded to the board by anadhesive, and a liquid crystal module is made in accordance withEmbodiment 5. A backlight 504 and a light guide plate 505 are providedon the obtained liquid crystal module. The liquid crystal module isthereafter covered with a cover 506. An active-matrix liquid crystaldisplay device such as that partially shown in section in FIG. 12 isthereby completed. The cover and the liquid crystal module are bonded toeach other by using an adhesive and an organic resin. When the plasticsubstrate and the opposed substrate are bonded to each other, a spacebetween the opposed substrate and a frame placed so as to surround theopposed substrate may be filled with the organic resin for bonding.Since the display device is of a half-transmission type, polarizingplates 503 are adhered to both the plastic substrate and the opposedsubstrate.

When a sufficient quantity of external light is supplied, the displaydevice is driven as a reflection type in such a manner that while thebacklight is maintained in the off state, display is performed bycontrolling the liquid crystal between the counter electrode provided onthe opposed substrate and the pixel electrodes (reflecting portions)502. When the quantity of external light is insufficient, the backlightis turned on and display is performed by controlling the liquid crystalbetween the counter electrode provided on the opposed substrate and thepixel electrodes (transmitting portions) 501.

However, if the liquid crystal used is a TN liquid crystal or an STNliquid crystal, the twist angle of the liquid crystal is changed betweenthe reflection type and the transmission type. Therefore, there is aneed to optimize the polarizing plate and the phase difference plate.For example, a need arises to separately provide an optical rotationcompensation mechanism for adjusting the twist angle of the liquidcrystal (e.g., a polarizing plate using a high-molecular weight liquidcrystal).

Embodiment 7

Various modules (active matrix liquid crystal module, active matrix ELmodule and active matrix EC module) can be completed by the presentinvention. Namely, all of the electronic equipments are completed byimplementing the present invention.

Following can be given as such electronic equipments: video cameras;digital cameras; head mounted displays (goggle type displays); carnavigation systems; projectors; car stereos; personal computers;portable information terminals (mobile computers, mobile phones orelectronic books etc.) etc. Examples of these are shown in FIGS. 13 and14.

FIG. 13A is a personal computer which comprises: a main body 2001; animage input section 2002; a display section 2003; and a keyboard 2004etc.

FIG. 13B is a video camera which comprises: a main body 2101; a displaysection 2102; a voice input section 2103; operation switches 2104; abattery 2105 and an image receiving section 2106 etc.

FIG. 13C is a mobile computer which comprises: a main body 2201; acamera section 2202; an image receiving section 2203; operation switches2204 and a display section 2205 etc.

FIG. 13D is a goggle type display which comprises: a main body 2301; adisplay section 2302; and an arm section 2303 etc.

FIG. 13E is a player using a recording medium in which a program isrecorded (hereinafter referred to as a recording medium) whichcomprises: a main body 2401; a display section 2402; a speaker section2403; a recording medium 2404; and operation switches 2405 etc. Thisapparatus uses DVD (digital versatile disc), CD, etc. for the recordingmedium, and can perform music appreciation, film appreciation, games anduse for Internet.

FIG. 13F is a digital camera which comprises: a main body 2501; adisplay section 2502; a view finder 2503; operation switches 2504; andan image receiving section (not shown in the figure) etc.

FIG. 14A is a mobile phone which comprises: a main body 2901; a voiceoutput section 2902; a voice input section 2903; a display section 2904;operation switches 2905; an antenna 2906; and an image input section(CCD, image sensor, etc.) 2907 etc.

FIG. 14B is a portable book (electronic book) which comprises: a mainbody 3001; display sections 3002 and 3003; a recording medium 3004;operation switches 3005 and an antenna 3006 etc.

FIG. 14C is a display which comprises: a main body 3101; a supportingsection 3102; and a display section 3103 etc.

In addition, the display shown in FIG. 14C has small and medium-sized orlarge-sized screen, for example a size of 5 to 20 inches. Further, tomanufacture the display part with such sizes, it is preferable tomass-produce by gang printing by using a substrate with one meter on aside.

As described above, the applicable range of the present invention isextremely large, and the invention can be applied to electronicequipments of various areas. Note that the electronic devices of thisembodiment can be achieved by utilizing any combination of constitutionsin Embodiments 1 to 6.

The film having thermal conductivity in accordance with the presentinvention dissipates heat produced by elements to limit degradation ofthe elements and to prevent deformation or and change in quality of atransfer member, e.g., a plastic substrate, thus protecting theelements. Also, the film having thermal conductivity in accordance withthe present invention prevents mixing of impurities such as water andoxygen from the outside to protect the elements.

Even if cracks are caused in the debonded layer at the time of debondingthe debonded layer from the substrate by a physical means, the crackedportions can be repaired by the film having thermal conductivity inaccordance with the present invention, thus improving yield as well asthe reliability of the elements.

1. A method of fabricating a semiconductor device comprising: forming ona first substrate a layer including a switching element; bonding asupporting member to the layer including the switching element;attaching a flexible printed circuit to a portion of the layer includingthe switching element; debonding the supporting member and at least apart of the layer including the switching element from the firstsubstrate with the flexible printed circuit being attached to the partof the layer including the switching element; bonding a film with thelayer including the switching element; and bonding a second substrate tothe film to interpose the layer including the switching element betweenthe supporting member and the second substrate, wherein the filmcomprises at least one of aluminum nitride, aluminum nitroxide, aluminumoxynitride, aluminum oxide and beryllium oxide.
 2. A method offabricating a semiconductor device according to claim 1, wherein a heattreatment or a treatment using irradiation with laser light is performedbefore debonding the supporting member and at least the part of thelayer including the switching element.
 3. A method of fabricating asemiconductor device according to claim 1, wherein the switching elementis a thin-film transistor having a crystalline semiconductor layer.
 4. Amethod of fabricating a semiconductor device according to claim 1,further comprising forming a liquid crystal material over the switchingelement.
 5. A method of fabricating a semiconductor device according toclaim 1, further comprising fixing the supporting member by covering aconnection between the flexible printed circuit and the layer includingthe switching element with an organic resin.
 6. A method of fabricatinga semiconductor device comprising: forming on a first substrate a layerincluding a switching element; bonding a supporting member to a firstportion of the layer including the switching element after forming onthe first substrate the layer including the switching element; attachinga flexible printed circuit to a second portion of the layer includingthe switching element; debonding the supporting member and at least apart of the layer including the switching element from the firstsubstrate with the flexible printed circuit being attached to the secondportion of the layer including the switching element; and fixing thesupporting member by covering a connection between the flexible printedcircuit and the layer including the switching element with an organicresin.
 7. A method of fabricating a semiconductor device according toclaim 6, wherein a heat treatment or a treatment using irradiation withlaser light is performed before debonding the supporting member and atleast the part of the layer including the switching element.
 8. A methodof fabricating a semiconductor device according to claim 6, wherein theswitching element is a thin-film transistor having a crystallinesemiconductor layer.
 9. A method of fabricating a semiconductor deviceaccording to claim 6, further comprising forming a liquid crystalmaterial over the switching element.